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<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script type="text/javascript">
        var a = 5;

        if(a % 2 == 0)
        {
            document.write("a是偶数");
        }
        else if(a % 2 !== 0)
        {
            document.write("a是奇数");
        }

    </script>
</head>
<body>
    
</body>
</html>